MOP - A MONODENTATE CHIRAL PHOSPHINE LIGAND FOR CATALYTIC ASYMMETRIC REACTIONS

Axially chiral monophosphines, 2-(diphenylphosphino)-2'-methoxy-1,1'-binaphthyl (MeO-MOP, 1a) and its biphenanthryl analog 5 were prepared starting with homochiral 2,2'-dihydroxy-1,1'-binaphthyl and 3,3'-dihydroxy-4,4'-biphenanthryl, respectively. The palladium complexes coordinated with the MOP ligands are highly effective catalysts for several types of catalytic asymmetric reactions where chelating bisphosphine ligands can not be used because of their low catalytic activity or low selectivity towards the desired reaction pathway. The catalytic asymmetric reactions are: 1) Asymmetric hydrosilylation of alkyl-substituted terminal olefins and bicyclo[2.2.1]heptene derivatives giving, after oxidation, optically active alcohols (similar to 95% ee). 2) Asymmetric 1,4-hydroboration of 1,3-enynes giving axially chiral allenylboranes (61% ee). 3) Asymmetric reduction of allylic esters with formic acid (up to 93% ee).